Emerge Australia uses ME/CFS as an umbrella term. Research has not confirmed whether the illness is one condition, two conditions (ME and CFS), several different conditions or a condition with several subgroups. ME/CFS includes all diagnoses of myalgic encephalomyelitis (ME), chronic fatigue syndrome (CFS), and ME/CFS.  The defining feature of ME/CFS is post-exertional malaise (PEM). 

ME/CFS has had many names. These names include post-viral fatigue syndrome, Royal Free disease and, most recently, systemic exertion intolerance disease (SEID). Debate remains as to the most appropriate name. This lack of consensus has contributed to confusion and skepticism about ME/CFS within the broader community. 

Emerge Australia does not endorse the use of the term ‘chronic fatigue’ as this is not an illness. Chronic fatigue is a symptom of many medical conditions, like cancer or multiple sclerosis. Chronic fatigue should not be used as a name for ME/CFS because it suggests the illness is primarily tiredness. People with ME/CFS experience a wide range of symptoms. These symptoms include, but are not limited to, profound fatigue.